#include <stdio.h>
 #include <stdlib.h>
 
 /* A short description of the function, if necessary
  */
 int main (int args, char *argv[]) {

    int *ptr; // here, star means pointer type
    int a = 5;
    
    ptr = &a; // ptr now had the value of the address of a.
    
    // Here, star means follow the pointer and access what is
    // at the end of it.
    printf( "a is %d and ptr points to %d\n", a, *ptr );
    printf( "ptr has the value %p\n", ptr );
    printf( "ptr is at address %p on the stack\n", &ptr );
    
    ptr = malloc( sizeof(int) );
    *ptr = 6;
    printf( "a is %d and ptr points to %d\n", a, *ptr );
    printf( "ptr has the value %p\n", ptr );
    
    // create a memory leak
    ptr = &a;
    
    ptr = malloc( sizeof(int) );
    *ptr = 7;
    printf( "ptr has the value %p\n", ptr );
    free( ptr ); // this time, free the memory first.
    
    // so now, the 7's spot is available for more mallocing but the
    // 6's spot never will be.
    // this should cause an error, but doesn't :(
    printf( "a is %d and ptr points to %d\n", a, *ptr );
    
    ptr = malloc( sizeof(int) );
    *ptr = 8;
    printf( "a is %d and ptr points to %d\n", a, *ptr );
    printf( "ptr has the value %p\n", ptr );
    
}